Gravity force absorber for use in certain parachute and other systems

ABSTRACT

A shock absorber assembly, particularly for attenuating shocks transmitted to a person&#39;s body, especially to reduce shock to a paratrooper&#39;s body during a tethered cargo tandem jump. Specialized elastic absorber units are disposed between two connectors, such as carabiners, with a connector secured to a respective end of each absorber unit. Each absorber unit has a rupture length corresponding to its length when it is stretched to its maximum immediately before rupturing under tensile loading. A limiter strap also is secured between the connectors, with a connector on each end of the limiter strap. The limiter strap prevents the absorber units from breaking by preventing their stretch to their breaking point. A flap or bands are provided for temporarily maintaining the limiter strap folded in a compact bale until needed. In use, the complete shock absorber assembly is deployed between a cargo tether and a cargo harness.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the filing of U.S. Provisional Patent Application Ser. No. 63/035,109 titled “Gravity Force Absorber for Use in Certain Parachute and Other Systems,” filed on Jun. 5, 2020, and of the filing of U.S. Provisional Patent Application Ser. No. 63/079,261 titled “Gravity Force Absorber for Use In Certain Parachute and Other Systems,” filed on Sep. 16, 2020, both specifications of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

This invention relates to shock absorbers, particularly for absorbing and dampening shocks due to certain parachuting, climbing, and rope access activities, and most specifically to a shock absorber for use with tethered tandem bundles, such as in certain military operations.

Background

People have been parachuting from aircraft, such as airplanes, helicopters, and balloons, for at least a hundred years. Parachuting is done for sport as well as for a variety of important utilitarian reasons. Non-sport, utilitarian parachuting is essential to certain military airborne missions, for example. Parachuting activity also sometimes is undertaken in selected law enforcement and/or search and rescue efforts and actions. In certain parachuting situations, principally in specialized airborne military special operations, there is a need for the person parachuting (hereinafter the “paratrooper”) from an aircraft to be accompanied directly by a sizeable cargo. “Cargo” herein refers to large bundles of equipment or materiel, not to include ordinary backpacks or auxiliary “belly-packs” releasably attached directly to the paratrooper's body. It is desired that the paratrooper and the cargo exit the aircraft at about the same time, and that the paratrooper and the cargo be connected together so as not to become distantly separated in the course of the air drop. It is known to have the cargo (which is typically contained in a cylindrical container) connected or “tethered” to the paratrooper, so that the cargo descends simultaneously with the paratrooper by means of a shared main parachute. A parachuting situation involving a paratrooper accompanied by a separate but connected cargo container sometimes is called a “tethered tandem bundle jump” or a “tandem cargo jump,” or similar.

A paratrooper wears a heavy duty main harness (including leg straps) to which the parachute system is reliably secured. The parachute system's main components are the main parachute assembly including the canopy, skirt, and suspension lines, and the links and risers which connect the suspension lines to the trooper's main harness. A tandem parachute system typically also includes a drogue chute (deployed shortly after exiting the aircraft) connected via bridle to the main parachute; the paratrooper pulls the drogue release which actuates the main parachute. In a tandem cargo jump scenario, the cargo container also is securely connected to the paratrooper's main harness by means of a high tensile strength tether, rope or cable. Thus, sometime after the main parachute has been deployed and the canopy opened, the cargo dangles below the paratrooper by means of the cargo tether, while the paratrooper is suspended below the main parachute canopy by means of the parachute system's suspension lines, links and risers, which are connected to the main harness attached on and around the trooper's torso and shoulders.

A significant, and potentially harmful, consequence of a tethered tandem bundle jump is the tremendous shock forces imparted to the falling paratrooper's body during the course of a jump. Even in an ordinary parachute jump with no large cargo bundle, a paratrooper is subjected to at least one significant shock, the “opening shock” of the rapid deceleration of the user's body resulting from the sudden braking effect of the opening of the main canopy. The magnitude of the opening shock is highly variable due to a variety of factors. Also, particularly in the case of a parachute jump involving the use of a static line (known in the art) to automatically deploy the parachute, the user may undergo a substantial “exit shock” when the static line reaches full extension (e.g., about twelve feet) to begin pulling upon the user's parachute system backpack. Besides increased opening and exit shocks, in a tethered tandem cargo jump, other potentially harmful shocks frequently are transmitted (via the cargo tether) to the user due to the added effects of the falling heavy cargo bundle. When a paratrooper undertakes a tethered tandem cargo jump, he and the cargo exit the aircraft at around the same time. The cargo container, however, often accelerates to fall faster due to its more aerodynamic shape and the relatively greater wind resistance upon the paratrooper; the paratrooper's body reaches terminal velocity sooner. Consequently, soon after leaving the aircraft and well before his main canopy has begun to open, the paratrooper frequently feels a first shock due to the cargo having fallen faster and reached the full extent of the cargo tether. The cargo tether, extending down from the falling paratrooper to the cargo below, is abruptly pulled taut by the weight of the falling cargo, as the slower-falling paratrooper curtails the velocity of the cargo. The resulting jolt is transmitted through the tether to the paratrooper's main harness and thus to the paratrooper's body. This first shock may be rapidly repeated one or more times (although at reduced magnitude) as the cargo “bounces” at the lower end of the tether. (It is desirable to damp the amplitude of such oscillatory bounces.) The paratrooper and cargo then continue falling together and at approximately the same speed (but not necessarily with the cargo tether completely extended). After some measured or selected time of free fall, the paratrooper actuates his parachute. Shortly after parachute deployment, the main canopy opens fully, and serves its purpose to slow the fall of the paratrooper's body. As the main canopy opens, the paratrooper falls further downward to the full length extent of the parachute's suspension lines and risers, and then experiences the “opening shock” common to all parachute jumps. However, in the instance of a tandem cargo jump, the cargo itself undergoes a separate deceleration due to the braking effect of the open canopy. This cargo opening shock is transmitted from the suddenly arrested cargo to the paratrooper's harness via the cargo tether. The magnitude of this cargo opening shock cannot be discounted, and can be quite large especially if the cargo is heavy and the cargo tether is anything less than taut at the time the paratrooper himself feels the initial opening shock. In some cases, the cargo falls a considerable distance in a short time after the paratrooper experiences canopy opening shock. This second or cargo opening shock, realized when the cargo tether again obtains its full extension and goes into tremendous tension, can convey a formidable jolt or shock force to the paratrooper.

The various shock forces described above are significant under ideal conditions, and can be enormously exaggerated by various factors including the weight, size, and aerodynamic shape of the cargo, the time period of free fall, the length of the cargo tether, the type of parachute system, winds aloft, etc. The shocks transmitted to a paratrooper's body can be, and have been known to be, harmful (even crippling) to paratroopers in the line of duty. Even skilled paratroopers using superior parachute systems, harnesses, and related equipment are prone to suffer adverse effects to their health—most especially to the muscles, bones, and connective tissues of their backs, necks, and shoulders—after having performed numerous tethered tandem bundle jumps in the course of years of dedicated service.

It likewise is true that there on occasion is a similar need to protect the cargo itself from the shocks and decelerations due to a parachute drop, including when the cargo is the object of an unmanned drop. As is known, various cargoes may be dropped by parachute from aircraft, unaccompanied by a human parachutist or paratrooper. Such cargoes may be of any of a wide variety of types and weights. It is always preferable, sometimes relatively important, to minimize the impacts and shocks of a parachute drop upon such a cargo. Thus, it is desirable to provide shock absorption for the cargo even when it is the parcel of an unmanned drop.

There is an unmet need to reduce the wear and tear on a paratrooper's body attributable to the shock forces associated with an airborne tethered tandem bundle jump. Likewise, shock absorption for an unmanned cargo drop is desirable. With the foregoing background, the presently disclosed invention was developed. Particularly, there is disclosed a system and apparatus for absorbing and attenuating the shock forces, including opening shock forces, transmitted to a paratrooper's body during the execution of a tandem cargo parachute jump. Moreover, an absorber assembly according to the present disclosure also can prolong the life and use of the entire parachute canopy system.

There also similarly is an unmet need to provide improved fall shock absorption, often called fall protection, in other contexts including military, recreational, and tactical situations. When a person is attached in a harness and engaged with a rope, and the rope may be a safety rope connected to an anchor point on a building, or the ground, or an aircraft, or the like, there is a need to absorb the shock to the user's body at the instant the rope arrests a fall, such as an accidental fall.

SUMMARY OF THE INVENTION

There is disclosed an absorber system for attenuating the shocks transmitted to a person's body. This system and apparatus are well-suited to attenuate or absorb the shock to a paratrooper's parachute harness, and thus to the trooper's body, during a tethered cargo tandem jump. Significantly, the present system serves to absorb or dampen deleterious shock forces throughout the full duration of a tethered tandem bundle jump, from the instant the user exits the aircraft to and including the moment he touches ground. One or more specialized resiliently elastic absorber units are disposed between two connectors, such as suitable carabiners or tri-link type carabiners, with a connector secured to a respective end of each absorber unit. Each elastic absorber unit is configured to stretch up to a pre-selected amount or distance in order to absorb a tensile load applied thereto. Each absorber unit has a rupture length corresponding to its approximate length when it is stretched to its maximum length immediately before rupturing under tensile loading. A limiter strap also is secured between the two connectors, with a connector such as a carabiner on each end of the limiter strap. The limiter strap prevents the absorber units from breaking by impeding their stretch to their breaking point. The limiter strap is capable of minimal stretching, and is less elastic than an absorber unit. The limiter strap has a predetermined maximum length (stretching only slightly longer than its nominal length at rest), being the length to which it can extend under tensile loading before it tears or breaks. The limiter strap's maximum length is shorter than the approximate rupture length (maximum breaking length) of the strongest absorber unit in the overall absorber system. The limiter strap has a minimum breaking strength in excess of the sum of the strengths of the one or more absorber units in the total shock absorber system.

Using the connectors, the absorber system is operatively disposed between a cargo container and the parachute harness of a user engaging in a tandem cargo parachute jump. For example, the absorber system may be installed just above the cargo, between a cargo tether and a cargo anchor or cargo harness. Other aspects, advantages, and applications are disclosed and claimed hereinafter, as this summary is not limiting of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The attached drawings, which form part of this disclosure, are as follows:

FIG. 1 is a side view of a person parachuting down through the air during a tethered tandem cargo jump, and illustrating generally a use of a system according to the present invention;

FIG. 2 is an enlarged perspective view of an absorber unit component, defining two fastener apertures therein, useable in the system and apparatus of the present invention;

FIG. 3A is a side or edge view of the absorber unit seen in FIG. 2 ;

FIG. 3B is a plan view of the absorber unit seen in FIG. 2 ;

FIG. 3C is a perspective view of an alternative embodiment of an absorber unit, defining four fastener apertures therein, useable in a system and apparatus according to the present invention;

FIG. 4A is a plan view of a limiter strap and wrap flap assemblage useable in the system and apparatus of the present invention, the strap and flap both being unfurled;

FIG. 4B is a side view of the limiter strap and wrap flap assemblage seen in FIG. 4A;

FIG. 4C is a perspective view of the strap and wrap flap assemblage seen in FIG. 4A;

FIG. 5A is a plan view of a preferred embodiment of a shock absorber assembly according to the system and apparatus of the present invention, showing three absorber units disposed between a pair of connectors, together with a limiter strap and wrap flap assemblage, and with a first connector disposed through a first looped end of the limiter strap;

FIG. 5B is a plan view of the shock absorber assembly seen in FIG. 5A, illustrating a folding of the limiter strap against itself to prepare the absorber assembly for use;

FIG. 5C is a plan view of the shock absorber assembly seen in FIG. 5B, illustrating a further double folding of the limiter strap into a “Z” or “S” arrangement to prepare the absorber assembly for use;

FIG. 5D is a plan view of the shock absorber assembly seen in FIG. 5C, showing that the limiter strap is fully folded, and a second connector is engaged through a second looped end of the limiter strap for use;

FIG. 5E is a plan view of the shock absorber assembly seen in FIG. 5D, showing the beginning of a rolling of the absorber units, connectors, and limiter strap within the wrap flap;

FIG. 5F shows that, per FIG. 5E, the rolling of the absorber units and limiter strap within the wrap flap is nearly completed, so that the absorber units and folded limiter strap are enveloped within the wrap flap and such that a complementary pair of hook-and-loop fabric fastening strips are about to be brought into fasting contact;

FIG. 5G is a view of the shock absorber assembly of FIGS. 5A-F arranged for use according to the invention, illustrating that the absorber units and folded limiter strap are wrapped within the wrap flap, the wrap flap temporarily held by releasable fasteners, and with the connectors available for use;

FIG. 6 is an overall view of certain key components of an embodiment of shock absorber assembly according to the present invention, with four absorber units and an unfolded limiter strap connected between two connectors (carabiners);

FIG. 7 is an overall view of the embodiment of shock absorber assembly seen in FIG. 6 , configured for use with the absorber units unstretched and the limiter strap held in a furled condition, with the shock absorber assembly engaged between a cargo multi-strap harness and a cargo tether;

FIG. 8 is a side view of a version of shock absorber assembly according to the present invention, shown stretched out while absorbing a shock, with absorber units elongated and the limiter strap unfurled, the assembly engaged between a cargo multi-strap harness and a cargo tether;

FIG. 9 illustrates a special arrangement of two absorber units between a pair of connectors;

FIG. 10 illustrates a special arrangement of three absorber units between a pair of connectors;

FIG. 11 is a view of the system according to the present invention, in use during a non-tandem, unmanned, parachute drop, to protect a cargo during the drop; and

FIG. 12 is a front view of a user with a system according to the present invention, there being a rope for securing the user to a safety anchor point, and including a shock absorber assembly configured for use to absorb the shock of a user's fall.

Like elements are labeled with like numerals in the several views; the drawings are not necessarily to scale, within a view or relative to each other.

DETAILED DESCRIPTION OF THE INVENTION

This invention relates to shock absorption, primarily to an apparatus system for absorbing and/or dampening the shocks to the body of a person parachuting from an aircraft. However, the invention may be put to other practical uses where shock absorption is desired, including fall protection for persons (e.g., persons rappelling), and shock absorption in unmanned cargo parachute drops. Further, a shock absorber assembly according to this disclosure may find use in the tying-down and security of cargo as with ropes and nets, or the like.

Nevertheless, the disclosed apparatus and system find specific use in the performance of a tethered tandem bundle parachute jump, in which a person parachuting from a flying aircraft is accompanied in the jump by a cargo bundle tethered to the user's parachute harness. Tandem cargo parachute jumps subject a person's body, particularly his or her spine, neck and/or shoulders, to one or more significant jolting forces due to the shocks associated with the operations of the parachute system and the presence of the added cargo load. Besides reducing shocks to the parachuting person's body, the present system also beneficially ameliorates corresponding and associated shocks to the cargo bundle and the user's parachute system overall. The present system is devised to decrease the severity of these shocks.

Currently, extra robust parachute systems, including reinforced canopies, may be required when a tandem bundle jump is to be undertaken. Use of the presently disclosed absorber assembly may eliminate the need to use such specialized heavy duty parachute systems, as reduced shocks are imparted to the chute system. A substantial advantage of the present apparatus and system is that they act to ameliorate shocks and jolts to a paratrooper throughout the duration of a tethered tandem cargo jump—from the initial “tether snatch” to touchdown landing.

Reference is made to FIG. 1 . In a tethered tandem bundle or cargo parachute jump, a parachute system 10 including a canopy 11 and suspension lines 12 slow the descent of the user 15 toward the surface of the Earth, generally in accordance with convention. The canopy 11 may be any type of canopy known or hereafter devised, including round, cruciform, or square/rectangular (e.g., ram air chute). The user 15 wears a known type of parachute harness which is secured to the parachute system 10 by means of risers (or equivalents); risers are strips of webbing (for example) joining the user's body harness and the rigging or suspension lines 12 of a parachute. The user 15 in this disclosure may be referred to as a “paratrooper,” but so identifying the user does not restrict the invention solely to military applications. The system or apparatus according to this disclosure may find application in any circumstance involving a tandem bundle type of parachuting activity.

In a tethered tandem bundle jump, as suggested in FIG. 1 , the paratrooper 15 is accompanied throughout the duration of the jump by a cargo 20. The cargo 20 typically is bundled or containerized in various ways known in this field of endeavor. In a typical military tethered tandem bundle jump, the cargo 20 may weigh as much as 300 pounds (lbs.), and often up to 700 lbs. The cargo 20 is flexibly and releasably, but reliably, connected to the paratrooper's body harness by means of a cargo tether 24, as known in the art. A cargo 20 may have a (currently known in the art) harness 22 attached thereto, or some other means or container anchor for connecting the cargo tether 24 to the cargo 20. Such a cargo harness 22 may have three or four (as shown) or more straps for a stable connection between the cargo and the single-line cargo tether 24. A tether 24 is fabricated from materials, and according to specifications, configurations, and tensile strengths and elasticity, known currently in the specialized field of tandem bundle parachuting operations.

As explained hereinabove, during the course and serial stages of a tandem bundle jump, the parachute system 10, the user 15 (via his harness), the tether 24, and the cargo 20 are all subjected to substantial forces, when the suspension lines 12 and the cargo tether 24 abruptly obtain full tension extension and suddenly transmit high forces in the parachute system and to the user and the cargo. A paratrooper 15 ordinarily feels first the force of the “tether snatch” as the cargo 20 is ejected from the aircraft immediately before the paratrooper, and a pulling force is transmitted by the cargo to the paratrooper's harness. Tensile forces and jolts to the paratrooper continue thereafter, in varying amounts, throughout the duration of a jump from exit to freefall, to opening shock, to under canopy, to landing. After the initial full extensions (and resulting shocks) of the suspension lines 12 (e.g., beneath an open canopy 11) and of the cargo tether 24 (which full extensions do not necessarily occur simultaneously), the paratrooper 15 may “bounce” up-and-down upon the flexible and somewhat elastic suspension lines 12, while the cargo 20 may also bounce at the end of the flexibly and somewhat elastic cargo tether 24. These “bouncing” movements result in further repeated, although relatively diminished, shocks to the user, parachute system, and cargo.

The shock absorber assembly according to the present disclosure, to be described in detail hereinbelow, is installed between the paratrooper 15 and the cargo 20, so as to reduce shocks that otherwise would be transmitted between the cargo and the paratrooper via the cargo tether 24. The present shock absorber assembly potentially can be provided anywhere in, on, or along the train of components connecting the cargo 20 to the paratrooper 15, so to attenuate tension forces otherwise transmitted via the cargo tether 24. Preferably, however, the inventive shock absorber assembly is installed at or near the juncture, at location SA in FIG. 1 , between the distal end of the cargo tether 24 and the cargo harness 22 (or other anchor to the cargo).

The present invention has been used advantageously to attenuate by approximately 20 percent the maximum forces transmitted though the parachute system as felt by the user or cargo. In one test, an 8 g acceleration was reduced by about 2 g.

Combined reference is invited to FIGS. 2-5 , which considered collectively illustrate basics of the shock force absorber, or shock absorber assembly 30, according to the present invention. The shock absorber assembly 30 includes four principal components: at least one absorber unit 32 and/or 32′, a limiter strap 34, and a pair of connectors 36. The connectors 36 most preferably are carabiners of construction and rating known in the field of tandem bundle parachuting, and may be of a “tri-link” type configuration. (“Tri-link” connectors in a highly technical sense are not true carabiners; a tri-link defines a somewhat triangular overall shape, a screwed closure, and is preferred when tri-axial loading is expected, while conventional carabiners are devised for uniaxial loading on their spine side. Herein, however, the term “carabiner” shall include tri-links.) Connectors 36 are repeatedly openable and closeable, such that they can be opened for releasable engagement through a loop or aperture, and closed in a manner to provide temporary yet secure such engagement, as rated carabiners conventionally are. A preferable connector is 36 an extra-large steel auto three-stage locking carabiner that exceeds National Fire Protection Association (NFPA) requirements; suitable connectors 35 are “XL Steel Triple Lock” carabiners available from Mad Rock Climbing of Santa Fe Springs, Calif., USA. Or, a “tri-link” useable as a connector 36 is the “Delta EN” Maillon Rapide® link available from Peguet SA, of Annemasse, France. The connector carabiners 36 ideally are of a “triple action” type, i.e., three deliberate manipulative steps are necessary to open a securely closed carabiner (to prevent accidental opening).

One or more (usually at least two, preferably three, rarely but sometimes four (e.g., FIGS. 6 and 7 )) absorber units 32, connected with at least one (ordinarily only one) limiter strap 34, by means of the two carabiners 36, constitute the basics of a shock absorber assembly 30 according to this disclosure. Two connectors, such as carabiners 36, are used in a complete shock absorber assembly 30; one on each end of the limiter strap 34 also engaged with a respective end of an absorber unit 32. A carabiner 36 is releasably but securely disposed through a loop 44 in a corresponding end of the limiter strap 34, and through a fastener aperture in a corresponding end of an absorber unit 32, to interconnect the limiter strap 34 and at least one absorber unit, in the manner suggested in FIG. 6 . Importantly, when used in the context of a manned tethered tandem bundle jump, at least two absorber units 32 always are used. A user may selectively adapt the shock absorption capacity of an absorber assembly 30 by choosing an appropriate number and kind(s) of absorber units 32 to be used in the assembly, as explained further herein. Two or three absorber units 32, 32′ (FIGS. 2, 3A, 3B and 3C) typically are used in a manned tethered tandem bundle jump. But four, or potentially even more, absorber units 32′ may be employed in a shock absorber assembly 30 particularly in unmanned cargo drops as seen in FIG. 11 .

FIGS. 2, 3A, and 3B illustrate one preferred embodiment of an absorber unit 32 according to the present disclosure. An absorber unit 32 is molded from a stretchable, resilient, elastic, and durable thermoplastic, such as polyurethane; polyurethane advantageously is resistant to saltwater and chemicals. The absorber unit 32 is devised to stretch axially a considerable amount when under tension, so as to resiliently absorb applied tension forces. Absorber unit 32 typically has an axial length (at rest) of from about 6 inches to about 10 inches, and preferably is approximately 8 inches long. As suggested by FIG. 3A, the unit 32 is generally “flat” in its side and end views, and relatively thin in its thickness dimension; the thickness dimension typically is between 0.24 inches and about 0.34 inches. It may be about two inches wide, e.g., at the greatest widths of its end attachment portions 38. The absorber unit 32 by general example can stretch axially to about 34 or 35 inches before breaking, that is, the maximum stretched length is about 35 inches when unit failure is imminent.

An absorber unit 32 preferably is axially symmetrical, and comprises two opposing end attachment portions 38 joined by a plurality of intermediate joinder sections 40 extending between the end attachment portions. The absorber unit 32 is integrally molded from polyurethane elastomer, so that the distal attachment portions 38 and the joinder sections 40 are a single structural unit. The unit 32 has at least two, up to six, and very preferably four parallel intermediate joinder sections 40. The joinder sections 40 may be generally cylindrical, and their ends are securely integrated with the attachment portions 38. The incorporation of a plurality of relatively thinner cylindrical intermediate joinder sections 40 (rather than, e.g., a single thick joinder trunk) promotes the proper thermo-molding of the joinder sections while retaining their collective tensile strength. Moreover, a plurality of thinner intermediate joinder sections promotes the lateral bendability of an absorber unit 32, facilitating its manual bending and manipulation by a user. (See, e.g., FIG. 9 .) As seen in FIGS. 2, 3B and 3C, the attachment portions 38 each defines in plan view a sort of trapezoidal, or broadly rounded triangular shape, having its narrower width dimension at the end of the absorber unit 32. This shape has been determined to provide good strength performance, while also facilitating the easy insertion and closure of releasable connectors, such as carabiners, through a fastener aperture 42 and around the attachment portion 38. Each attachment portion 38 may have reinforcement ribs (not shown) corresponding to and in registration with the joinder sections 40. Each attachment portion 38 also preferably has a reinforcing rib running along its periphery, as indicated in FIGS. 2 and 3B. In this version of the absorber unit 32, each of the two attachment portions 38 is penetrated, near its center, by a fastener aperture 42 through which a connector carabiner 36 may be disposed.

Alternative versions of the absorber unit 32 may have more than two fastener apertures 42; FIG. 3C shows that, in alternative embodiments, an absorber unit 32′ defines two fastener apertures in each corresponding attachment portion 38. There are seen in FIG. 3C two inner fastener apertures 42 a and two outer fastener apertures 42 b, with one of each defined through respective attachment portions 38 of the absorber unit 32′. Having four fastener apertures 42 a,b in an absorber unit increases the versatility of the system, allowing a user to select from a variety of absorber units 32, 32′ to customize the performance of the user's completed absorber assembly 30 to the demands of a particular tethered tandem bundle jump or other circumstance.

An absorber assembly 30 may include one or more absorber units selected from either or both of two types of absorber units 32 or 32′. The types are differentiated by, among other things, their elastic elongation response to tensile shock loading. To increase versatility of the system to adapt an assembly 30 to the expected demands of a particular circumstance, an absorber unit may be either “high-stretch” absorber unit 32 (e.g., FIG. 2 ) or a “low-stretch” absorber unit 32′ (e.g., as seen in FIG. 3C).

An exemplary low-stretch absorber unit 32′ is molded from polyurethane elastomer with a tensile strength of about 6,400 psi, and potentially capable of about 430% elongation. Such a low-stretch absorber unit 32′ preferably is nominally about eight inches long at rest, and between about 0.25 and about 0.31 inches thick (e.g., the intermediate joinder sections 40 may be 0.25 inches thick, while the attachment portions 38 may be about 0.31 inches thick (as seen in FIG. 3A)). An exemplary high-stretch absorber unit 32 is also molded from polyurethane elastomer with a tensile strength of about 5,500 psi, and is capable of about 500% elongation. Such a high-stretch absorber unit 32 also preferably is nominally about eight inches long, and between about 0.24 and about 0.34 inches thick (e.g., the intermediate joinder sections 40 may be 0.24 inches thick, while the attachment portions 38 may be about 0.34 inches thick).

A marked advantage of the invention is that the number and type of absorber units 32 or 32′ employed in an absorber assembly 30 can be selected to devise a constructed assembly 30 having a predetermined amount of stretch under a given tensile loading force. An approximate but reliably predictable elongation response accordingly can be set at the time the absorber assembly 30 is compiled. Table 1 immediately below tabulates the amount, in inches, that an absorber assembly 30 composed of a “stack” of one, two, or three low-stretch absorber units 32′ may be expected to elongate under a given force. For example, referring to Table 1, an absorber assembly 30 incorporating only a single low-stretch absorber unit 32′ (e.g., nominally eight inches long) can be expected to stretch by about two additional inches (to an extended length of ten inches) under a shock force of 2.17 kilonewtons (kN) (490 lbs.). Or, as also shown in Table 1, an absorber assembly 30 featuring three low-stretch absorber units 32′ (eight inches long at rest) can be expected to stretch by about seven additional inches (to an extended length of fifteen inches) under a shock force of 11.25 kN (2,530 lbs.).

TABLE 1 STRETCH LENGTH TO TENSION FORCE, LOW-STRETCH ABSORBERS Stack of One Stack of Two Stack of Three Additional 8-inch 8-inch 8-inch Elongation Low-Stretch Low-Stretch Low-Stretch (inches) Absorber Unit Absorber Units Absorber Units 1 1.86 kN 420 lbs. 3.95 kN 890 lbs.  5.91 kN 1330 lbs. 2 2.17 kN 490 lbs. 4.75 kN 1070 lbs.  7.16 kN 1610 lbs. 3 2.53 kN 570 lbs. 5.56 kN 1250 lbs.  8.00 kN 1800 lbs. 4 2.84 kN 640 lbs. 5.96 kN 1340 lbs.  8.8 kN 1980 lbs. 5 3.15 kN 710 lbs. 6.45 kN 1450 lbs.  9.43 kN 2120 lbs. 6 3.46 kN 780 lbs. 6.89 kN 1550 lbs. 10.27 kN 2310 lbs. 7 3.78 kN 850 lbs. 7.56 kN 1700 lbs. 11.25 kN 2530 lbs. 8 3.95 kN 890 lbs. 8.05 kN 1810 lbs. 12.01 kN 2700 lbs.

Any given absorber unit 32 or 32′ has a known approximate maximum breaking length. A single low-stretch absorber unit 32′ preferably has a minimum breaking strength (rupture failure) of 4.98 kN (1,120 lbs.) and a maximum breaking length of between about 25.5 inches and about 26.5 inches. Thus, a low-stretch absorber unit 32′ which has a nominal length (at rest) of about 8 inches, may elongate up to about 26.5 inches before failing. As seen in Table 1, a single low-stretch absorber unit 32′ will stretch an additional 8 inches under an 890 lbs. load. Two low-stretch absorber units “stacked” in combination preferably have a minimum breaking strength of 9.29 kN (2,090 lbs.) and the same maximum breaking length of about 25.5 inches to 26.5 inches.

In a like manner generally, Table 2 below tabulates the amount, in inches, that an absorber assembly 30 composed of a “stack” of one, or of two, high-stretch absorber units 32 may be expected to elongate under a given force. For instance, an absorber assembly 30 incorporating a single high-stretch absorber unit 32 (eight inches long at rest) can be expected to stretch by about five additional inches (to an extended length of thirteen inches) under a shock force of 0.75 kilonewtons (kN) (170 lbs.). As also shown in Table 2, an absorber assembly 30 including two high-stretch absorber units 32 (eight inches long at rest) can be expected to stretch by about twenty additional inches (to an extended length of 28 inches) under a shock force of 4.98 kN (1,120 lbs.).

TABLE 2 Additional Stack of One Stack of Two Elongation High-Stretch High-Stretch (inches) Absorber Unit Absorber Units 5 0.75 kN 170 lbs. 1.69 kN  380 lbs. 10 1.06 kN 240 lbs. 2.31 kN  520 lbs. 15 2.53 kN 360 lbs. 3.46 kN  780 lbs. 20 2.44 kN 550 lbs. 4.98 kN 1120 lbs.

A single high-stretch absorber unit 32 preferably has a minimum breaking strength (rupture failure) of 3.06 kN (690 lbs.) and a high-stretch absorber unit maximum breaking length of between about 34.0 inches and about 35.0 inches. Two high-stretch absorber units “stacked” in combination preferably have a minimum breaking strength of 6.22 kN (1,400 lbs.) and the same maximum breaking length of about 34.0 inches to 35.0 inches. Table 2 shows that a single high-stretch absorber unit 32 will stretch an additional 20 inches under a 550 lbs. load.

From all the foregoing, a person of ordinary skill may selectively “mix and match” from a number of absorber units 32 and/or 32′ to assemble a shock absorber assembly 30 having a predetermined elongation and absorption response under an anticipated shock loading force. If an absorber unit 32 fails during use, such failure probably occurs with breakage of the joinder sections 40. During operation of the absorber assembly 30, if the joinder sections 40 fail at all, they likely rupture serially at different times, which contributes to a less sudden or violent failure (with diminished catastrophe).

Also included in the absorber assembly 30 is a limiter strap 34 seen in FIGS. 4A-C and also depicted basically and diagrammatically in FIGS. 6 and 7 . The limiter strap 34 is a “backup” to the absorber units 32, 32′, serving to prevent the separation of the cargo 20 from the paratrooper 15 in the unlikely event that all the absorber units in an assembly 30 rupture and completely fail during the course of a jump. The limiter strap 34 preferably is a woven nylon web strap, sewn to define a fastener loop 44 at each end thereof. The two loops 44 when opened may have diameters of, for example, about 1.5 to about 2 inches. The reinforcing sewing 48 is according to known techniques and ratings to maintain the functional strength of the limiter strap 34. As suggested in FIG. 4C, each of the two loops 44, at opposite ends of the limier strap, may also have a sewn reinforcement 45 at its extremity. The limiter strap 34 preferably is mildly stretchable, and has an ultimate breaking strength of at least 6,000 lbs. and very preferably at least 10,000 lbs. (about 45 kN). The limiter strap 34 may be about 1.75 inches wide. Referring still to FIG. 4A, in a preferred embodiment the limiter strap 34 has a nominal length L of approximately 17.5 inches, with a maximally extended (stretched while under tensile loading) length of about 19.5 inches. It is noted, therefore, that the maximum length of the limiter strap 34 is less than the maximum breaking length of a single high-stretch absorber unit 32 (i.e., 19.5 inches is less than 35 inches), and is also less than the maximum breaking length of a single low-stretch absorber unit 32′ (i.e., 19.5 inches is less than 26.5 inches). (As set forth in Table 1, a single low-stretch absorber unit 32′ extends to 16 inches (nominal eight inches length plus eight inches additional stretch under an 890 lbs. load, while Table 2 reveals that a single high-stretch absorber unit 32 extends to 28 inches (nominal eight inches length plus 20 inches additional stretch under a 550 lbs. load).) Thus, the limiter strap 34, as a component of the complete absorber assembly 30, prevents the absorber units 32, and/or 32′ from stretching to their respective maximum breaking lengths. (When the limiter strap 34 is fully extended to its maximum length, loads are transmitted between the pair of carabiners 36 by the limiter strap 34, not by the absorber unit(s) 32, 32′.) The limiter strap 34 thus safeguards against failure of the absorber units of an absorber assembly 30 during use.

FIG. 6 illustrates a fundamental absorber assembly 30. The limiter strap 34 and the (e.g., in FIG. 6 , four) absorber units 32 are operatively interconnected by means of the pair of carabiners 36. A first carabiner 36 is opened, disposed through a first loop 44 on one end of the limiter strap 34, inserted through the fastener aperture(s) 42 in first end attachment portion(s) 38 of one or more absorber units 32, and then securely closed so to reliably connect the first end of the limiter strap to the first ends of the absorber units. (In a preferred embodiment of the assembly 30, three absorber units 32 are deployed, but the number of absorber units is selected by the user to suit the circumstance of use.) The second, other, carabiner 36 is opened, disposed through the other, second, loop 44 on the second end of the limiter strap 34, inserted through the other fastener aperture(s) 42 in second end attachment portion(s) 38 of the one or more absorber units 32, and also securely closed so to connect the second end of the limiter strap to the second ends of the absorber units. The limiter strap 34 at this point is slack and flaccid in relation to the absorber units 32. (Again, the overall length (e.g., 25 inches) of the limiter strap 34 exceeds the normal unstretched lengths (e.g., 8 inches) of the absorber units 32.

For use in a jump, it is preferable that the limiter strap 34 be bundled alongside the absorber units 32 so as not to freely flap about or snag on objects. Accordingly, it is preferred that the limiter strap 34 be folded, wadded, or otherwise clumped into a compact bale, and so maintained, until needed. Attention is invited to FIG. 7 , illustrating an absorber assembly 30 as configured for use in cooperation with the cargo tether 24 and the cargo harness 22 (or another suitable anchor directly upon the cargo 20). (See also FIG. 1 .)

FIG. 7 shows that the limiter strap 34 in a completed absorber assembly 30 preferably is doubled or Z-folded at least one or two times, concertina-like, against itself into compact bale. The term “compact” here suggests that the limiter strap is folded one or more times in a serpentine manner so that its nominal length is reduced to an apparent length roughly approximating the shorter nominal length of an absorber unit. For example, about 9.5 to 10 inches of “slack” in the limiter strap 34 is doubled back on itself, so that the strap compact bale has a reduced apparent length of about eight inches, which is about the same length as the absorber units 32. So configured, the limiter strap 34 is unobtrusive, and promotes the overall compact size and easy manipulation of the complete absorber assembly 30 in use.

There preferably is provided means for releasably maintaining the folded limiter strap 34 in the compact bale. For example, one or more bands 46 of frangible or tearable tapes or strips composed of any readily breakable material (e.g., rubber, plastic, lightweight fabric or polymer, paper, or the like) may serve as such means for releasably maintaining. The frangible holder bands or strips 46 are wrapped around the limiter strap bale, and maintain its compact condition until such time as the absorber units 32 are significantly stretched. When the absorber units 32 elastically elongate substantially—as during their function to absorb a tensile shock transmitted to the absorber assembly 30 from the harness 22 and/or tether 24—the holder bands 46 break or loosen, thereby freeing the limiter strap 34 to unfold and extend toward its full functional length L. Again, the exact composition or dimensions of the bands 46 is not critical, provided that the bands hold the limiter strap 34 in its compact condition during storage and ordinary handling prior to a parachute jump, but are capable of being rent by the forces transmitted to the limiter strap associated with the elongation of the absorber units 32 during shock absorption.

Alternatively to the use of separate holder bands 46, the z-folded limiter strap 34 may be maintained as a compact bale by means of stitching. In this version of the releasably maintaining means, the strap 34 is doubly folded against itself as suggested by FIG. 7 , and the overlapping portions or segments thereof are sewn together with frangible thread. The stitching through the overlapped sections of the limiter strap 34 manifests adequate strength to maintain temporarily the compact bale during normal handling prior to a parachute jump, but (similarly to the bands 46) are capable of being rent, ruptured, or displaced the by forces imparted to the strap 34 during the function of the absorber units 32.

Attention is returned to FIGS. 4A-C, which depict a preferred means for releasably maintaining the folded limiter strap 34 in the compact bale. This embodiment has a limiter strap 34 and wrap flap 47 assemblage for use in a shock absorber assembly 30. In this preferred embodiment, the limiter strap 34 is accompanied by a wrap flap 47. An edge of the wrap flap 47 is sewn or otherwise secured along a substantial portion (e.g., about 5.75 inches to about 6.5 inches) of the length L of the limiter strap 34, as indicated in FIGS. 4A and 4C. The wrap flap 47 may have dimensions of about 6.5 inches (corresponding to its juncture with the limiter strap 34) and about 10.5 inches (extending perpendicularly from the strap), and may be composed of 400 denier pack cloth. The wrap flap 47 is provided along the outer edge of its first side with a first fastener 49, and at an intermediate position upon its second side (underside in FIG. 4A) with a complementary second fastener 49′. The fasteners 49, 49′ preferably are complementary hook-and-loop fabric fasteners, such as VELCRO® fasteners, permitting the first side of the wrap flap 47 to be releasably fastened to its second side, as described further herein. Alternative kinds of releasable fastener means, such as selected types of ball-and-socket snaps, may also be adapted to the apparatus.

In the preferred embodiment of FIGS. 4A-C, the wrap flap 47 serves the purpose of the holder band(s) 46 described previously in consideration of FIG. 7 ; i.e., when rolled up and releasably secured by its fasteners 49, 49′, the flap 47 temporarily holds the limiter strap 34 in a folded bundle until it is deployed during use of the shock absorber assembly 30 (when the absorber units 32, 32′ undergo absorbing stretch). Furthermore, when wrapped around the absorber units 32, 32′, the flap 47 protects the absorber units against damage and the elements (sunlight, cold).

FIGS. 5A-G are temporally serial views of the limiter strap and wrap flap assemblage of FIGS. 4A-C as utilized to compile a shock absorber assembly 30 for ultimate use. The wrap flap 47 is wrapped around a folded limiter strap 34 and absorber units 32 (three units shown) to provide a completed and bundled shock absorber assembly 30. Referring to FIG. 5A, it is seen that three absorber units (32 and/or 32′) are disposed between two carabiners 36 as described previously. The limiter strap 34 is unfolded, and the flap 47 is unfurled. A first (upper in FIG. 5A) connector carabiner 36 is disposed through and secured in a first loop of the limiter strap 34. The limiter strap 34 is then folded (without twisting) against itself two times in a “Z” or “S” fold (as discussed previously herein with reference to FIG. 7 ), as indicated by FIGS. 5B and 5C. In FIG. 5C, the “Z” fold in the limiter strap 34 is being completed, so that the effective length of the strap is about the same as the adjacent length of the wrap flap 47. Then, in FIG. 5D, the second, “bottom”, carabiner 36 is releasably but reliably engaged through the other or second, bottom end loop 44 of the limiter strap 34. FIG. 5E shows that the user then rolls the folded strap 34 and absorber units 32, 32′, together with the pair of carabiners 36, within the flap 47. The rolling action is continued thereby to wrap the flap 47 around the bundled limiter strap and absorber units, as indicated in FIG. 5F. When the wrap is completed, the first fastener 49 and second fastener 49′ are brought into adjacent contact (incipiently suggested in FIG. 5F) and engaged together to releasably maintain the flap 47 in its position enveloping the limiter strap 34 and absorber units 32, 32′. FIG. 5G shows the shock absorber assembly 30 wrapped into a compiled bundle; the VELCRO strips on the flap 47 are engaged together to hold together the entire bundle including the carabiners 36, strap 34, and plurality of absorber units 32, 32′.

It is understood that when a shock absorber assembly 30 according to the embodiment of FIGS. 4A-C and FIGS. 5A-G is activated during a jump or fall, the fasteners 49, 49′ disengage and separate to permit the wrap flap 47 to unfurl, and the limiter strap 34 to unfold and extend, and the absorber units 32, 32′ to stretch, as shall now be further explained.

Reference is returned to FIG. 7 . It there is seen that the completed absorber assembly 30 is installed for use between the cargo tether 24 and the cargo harness 22. The absorber assembly 30 preferably but not necessarily is situated for use in the vicinity of the location SA identified in FIG. 1 . The operative connection of the absorber assembly 30 to the cargo tether 24 is by means of the first, upper, carabiner 36 in FIG. 7 ; the carabiner 36 being disposed through and closed around a secure terminal loop (or other suitably reliable attachment) in the tether 24. Similarly, the operative connection of the absorber assembly 30 to the cargo harness 24 is by means of the second, lower, carabiner 36, the second carabiner 36 being disposed through, and closed around, terminal loop(s) in the harness 22 (or by other suitably reliable attachment to some anchor or connection on the cargo 20). A suitable, adequately rated swivel connector (not shown) may be connected inline between the cargo tether 24 and the upper carabiner 36 to reduce undesirable twisting during use, if desired. Similarly or alternatively, a swivel may be connected between the cargo harness 22 and the second lower carabiner 36.

A primary function of the shock absorber assembly 30 apparatus according to this disclosure is illustrated by FIG. 8 . When a shock due to and during a tethered tandem cargo parachute jump creates/increases tension in either the cargo harness 22 or the cargo tether 24 or (normally) both of them, the force is transmitted to and absorbed or ameliorated, at least in part, by the absorber assembly 30. The shock force(s) are depicted by the directional arrows associated with the cargo harness and cargo tether in FIG. 8 . Shock forces are imparted to both the cargo tether 24 and the cargo harness 22, not necessarily precisely simultaneously, but nearly concurrently and surely in rapid succession. Such forces inevitably are transmitted from the tether 24 to the parachuting user 15 via his or her harness.

When tensile shock is transmitted from the cargo harness 22 and/or the cargo tether 24 to the absorber assembly 30, the absorber units 32, 32′ receive the forces (via the carabiners 36) and stretch longitudinally to attenuate the shock. The absorber units 32, 32′ undergo rapid axial stretching, and may stretch up to nearly their maximum breaking length, as suggested by FIG. 8 . As the absorber units 32 and/or 32′ stretch, the wrap flap 47 (or, alternatively the holder bands 46 (or holder stitches)) around the baled limiter strap 34 and around the absorber units unfurls (or fail), releasing the limiter strap to freely unfold. In the wrap flap embodiment of FIGS. 4A-C, the flap 47 is wrapped around the folded strap 34 and around the stretchable absorber units 32, 32′ and releasably secured by the complementary fasteners 49, 49′, until the time when the absorber units stretch under the tensile load thereby to cause the strap to unfold and the complementary fasteners to mutually detach. Thus, when the shock absorber assembly 30 receives its first substantial shock loading, the VELCRO® fasteners 49, 49′ mutually detach, causing the flap 47 to unroll and release the limiter strap 34, which can then unfold and fully extend as seen in FIG. 8 . Continued loading of the absorber assembly 30 causes the absorber units 32, 32′ to continue stretching elastically to reduce the shock forces transmitted to the user 15, his parachute system 10, and to the cargo 20.

In the event the shock force(s) are sufficiently great to strain and lengthen the absorber units 32, 32′ to a length exceeding the nominal length L of the limiter strap 34, the limiter strap extends and goes into tension. This condition is indicated in FIG. 8 , with the strap 34 and the absorber units 32, 32′ all having obtained the limiter strap's nominal length L. As explained hereinabove, the absorber units 32, 32′ preferably are specified to have a maximum breaking length that is greater than the maximum length of the limiter strap 34. With any additional loading on the shock absorber assembly 30, the limiter strap 34 thereafter extends further up to its maximum length, thereby to prevent any further elongation of the absorber units. At such an instant, continued or additional shock forces are transmitted to and through, and assumed by, the limiter strap 34 in addition to — or in the extreme circumstance of premature failure of all the absorber units, instead of — the absorber units 32. By means of the limiter strap 34 one, some, or typically and preferably all the absorber units 32, 32′ are prevented from surpassing their maximum axial breaking length, thereby averting their rupture. Moreover, in the unfortunate event all the absorber units 32, 32′ break under an extreme tensile load, the much stronger (e.g., rated strength 10,000 lbs.) limiter strap 34 remains intact to accept and bear the loads formerly borne by the absorber units. The limiter strap 34 thus serves as a failsafe interconnection means between the cargo tether 24 and the cargo harness 22. The limiter strap 34 accordingly safeguards against the cargo 20 becoming entirely detached and separated from the paratrooper 15 in the undesirable event of complete failure the absorber units 32, 32′ of the absorber unit 30.

After the shock forces (which may be repeated and of variable magnitude during the course of a single jump) have been absorbed by the absorber units 32, 32′, the absorber units (if intact) elastically rebound toward their rest condition and shape (as seen in FIGS. 2 and 3C). So long as the paratrooper 15 is aloft and the weight of the cargo 20 pulls down upon the absorber assembly 30, the absorber units may remain stretched somewhat by the weight of the cargo 20. (The limiter strap 34 is flaccid, if/while the absorber units 32 and/or 32′ bear all the weight of the cargo.) At a later time in the jump while the paratrooper 15 is drifting in descent under a full canopy 11, the combined system including the parachute system 10, the paratrooper 15, the tether 24, and the harness 22 and cargo 20 nearly obtain a condition of internal dynamic equilibrium, which continues till the cargo 20 contacts the ground.

After the jump is completed, the shock absorber assembly 30 may subsequently be repaired/restored for re-use by recompiling the limiter strap 34 (i.e., per FIG. 7 ). For safety reasons, re-use of the absorber assembly, and particularly the absorber units, should be limited (up to about five total jumps, for example) or preferably even avoided due to the repeated strains each use imparts to the components thereof. Regardless of whether any deformations or damage are observed, an absorber system 30 should be retired after a few uses to safeguard against potentially harmful failure.

Attention is advanced to FIGS. 9 and 10 , showing how the components of a shock absorber assembly 30 may be alternately configured to adapt and account for certain situations. (In FIGS. 9 and 10 , the limiter strap 34 and the wrap flap 47 (or frangible holder bands 46) are eliminated from the views of a shock absorber assembly for the sake of clarity of illustration.) Specifically, the absorber units, especially the low-stretch absorber units 32′ having four fastener apertures 42 a, 42 b (see FIG. 3C) can be deployed with carabiners 36 engaged with either the inner fastener apertures 42 a or the outer fastener apertures 49 b. The versatility of a shock absorber assembly 30 including these variations accordingly is improved, and may be especially adapted to situations where, e.g., a large shock loading is expected to be preceded by one or more relatively milder loads. FIG. 9 illustrates that in a shock absorber assembly, the carabiners 36 are engaged through the two inner fastener apertures 42 a of a first absorber unit 32′, while the same two carabiners are engaged through the outer fastener apertures 42 b of a second absorber unit 32′. Accordingly, when the counterpart shock absorber assembly incorporating the arrangement of FIG. 9 is subjected to tensile loading, the first absorber unit (on the right in FIG. 9 ) is the first absorber unit to bear and absorb the applied load. Only after the first absorber unit has stretched somewhat under the applied load does the second absorber unit (having the carabiners 36 disposed through its outer fastener apertures 42 b) begin also to assume the load. Thus, initial relatively small loads are absorbed only by the first absorber unit, sparing the second absorber unit until the applied load exceeds a certain threshold. Subsequently to such load threshold having been surpassed, both the first and the second absorber units assume and absorb the higher load forces, with the first absorber unit undergoing the comparatively greater strain and stretch.

FIG. 10 depicts a similar arrangement, except that two absorber units 32′ (i.e., second and third absorber units) have the carabiners 36 engaged with their aligned outer fastener apertures 42 b, while the first absorber unit 32′ has the two carabiners engaged inner fastener apertures 42 a. The arrangement of FIG. 10 accordingly is adapted to receive and absorb larger subsequent loads after the initial loading absorbed solely by the lone first adapter unit.

The configurations seen in FIGS. 9 and 10 are particularly useful when it is desired to incrementally receive and absorb a series of two or more shock loads of temporally increasing force. The force-to-stretch characteristics of the absorber units 32′ may be preselected (e.g., per the data of Table 1 above) to predetermine the overall performance of a completed shock absorber unit 30. An example of practical utility is the case of a tethered tandem bundle jump, where an initial, relatively smaller “tether snatch” force is encountered and felt by a user 15 when the cargo 20 is first released from the aircraft, and is then soon followed by comparatively greater shocks due to canopy “opening shock” and subsequently repeating and varying, but large, load forces generated while the tandem of paratrooper and cargo descend to the ground. The initial tether snatch force may be absorbed by the single first absorber unit 32′ only, reserving the actuation and absorptive elongation of the second (and third) absorber units 32′ (with carabiners 36 disposed through their outer fastener apertures 42 b) for subsequent and greater shocks.

A user may also make selected varying use of the inner 42 a or outer 42 b fastener apertures, and differing numbers of absorber units 32′, in a shock absorber assembly 30 to customize its load bearing capacity or shock absorption response characteristics. By way of further explication, the two-absorber unit arrangement of FIG. 9 may be desirable for use with a tethered tandem cargo 20 of less than 500 lbs. In such an instance, because only the one first absorber unit 32′ absorbs the tether snatch force, the user 15 feels a lesser shock than if a stack of two or more (thus less “stretchable”) absorber units were concurrently receiving and transmitting to the user the tether snatch force. Yet, the arrangement of FIG. 9 still provides adequate tensile strength and ultimate shock absorption capacity for the increased total loads generated later during the jump. Similarly, the three-absorber unit arrangement of FIG. 10 may be desirable for use with a tethered tandem cargo 20 of greater than 500 lbs. The initial, milder, snatch force is absorbed only by the first absorber unit 32′ resulting in a lesser shock to the user, while the second and third absorber units 32′ are nonetheless available to receive, in functional combination with the first absorber unit 32′, the much greater total loads resulting from larger shocks (e.g., canopy opening shock and later bounces and jolts) generated later during the jump. If necessary, a fourth absorber unit 32′ could be added with the carabiners 36 engaged with its outer fastener apertures 42 b, to adapt a shock absorber assembly 30 to safely accommodate an even heavier cargo 20.

Attention it turned to FIG. 11 , illustrating the deployment of the shock absorber assembly 30 in an unmanned parachute drop of a cargo 20. The principles disclosed hereinabove with reference to FIGS. 1-10 apply generally in this embodiment of the invention, except that the human user 15 and his personal gear are removed from the system. Rather, the shock absorber assembly 30 as described previously is used to absorb shocks imparted to a cargo 20 of a non-tandem, that is, unmanned, parachute drop. The system 10 includes the canopy 11 and suspension lines 12 as described above, which lines 12 converge to a connection link assembly 80 known or suitable to the art. The cargo tether 24 descends directly from the link assembly 80 to the location SA where the afore-described shock absorber assembly 30 connects (e.g., by a durable loop or link, including optionally a mechanical swivel link) the bottom end of the tether to the collected top ends of the multi-strap harness 22. The distal or bottom ends of the straps of the harness 22 are secured to the cargo 20. For example, the harness 22 may be securely engaged with loops (not shown) attached to the top of a cargo bin or barrel, or to a flexible net-like assembly (not shown) which receives and cradles the cargo 20 in a manner known in the art.

It is apparent, therefore, that the shock absorber assembly 30 is positioned to receive and absorb any of the various shocks (including opening shock, etc.) transmitted from the parachute system to the cargo via the tether 24.

Human Fall Shock Absorption Generally

A person skilled in the art recognizes that the shock absorber assembly 30 according to this disclosure also may find practical utility in the field of personnel fall shock absorption/attenuation generally. To conduct high angle (steep climb and descent rappel) climbing operations, such as in mountaineering and rock climbing, but also including in tactical assaults or rescues in buildings, or while free rappelling or otherwise descending from an aircraft (such as a helicopter) users (climbers, rescue technicians, military personnel, tactical operators, law enforcement, etc.) may wear a climbing harness system. Falls from the rear openings of military helicopters also are of a concern. Climbing harness systems have been devised for use by recreational climbers, as well as for use by military and law enforcement personnel. Similar requirements arise in the event of urban assaults, searches, and rescues on cliffs or steep mountainous terrain. To perform high angle maneuvers using climbing ropes, a user must be equipped with some sort of climbing belt or harness by which the user removably and controllably engages with the climbing rope or ropes deployed in the operation. There are a wide variety of harnesses and belts known for use in tactical, rescue, and recreational operations. One known type of harness system is disclosed, for example, in my U.S. Pat. No. 6,481,528, the teachings of which are incorporated herein by reference.

The present shock absorber assembly 30 alternatively relates to general industry fall protection. Falls are among the most common causes of serious work-related injuries and deaths. Employers must take measures in their workplaces to prevent employees from falling off overhead platforms, elevated workstations or into holes in the floor and walls.

A person using a rope and harness system may the long rope attached or anchored, by any of a variety of means or modes, to a secure point, such as on a building, rock, or hovering helicopter. This anchor is, of course, for safety purposes; should the user accidentally fall, his descent is arrested by the rope between his harness and the anchor point becoming taut, so that at the time the fall is stopped, the resulting force of the arrested fall is transmitted from the user to the anchor point. The user does not fall any further than the amount of slack rope between her harness and the anchor point, thus preventing a much longer, potentially fatal, fall. However, at the time the fall is stopped, the user experiences an impact force or “fall force,” which force may be significant and potentially harmful. A safety limit for the fall force is conventionally given to be 12 kN, a limit above which the force can be potentially fatal. It is most desirable to keep the impact or fall force below about 8 kN, above which the force usually causes injury. It is accordingly desirable to provide a shock absorber within the rope and harness system to reduce the magnitude of the fall force felt by the user. The shock absorber assembly 30 accordingly may be adapted and deployed for providing shock absorption in operative combination with a rope system used in climbing, rappelling, and like operations. The climbing ropes are interconnected with a shock absorber assembly 30 as described hereinabove, and which absorbs an impact force in the event of a fall, particularly an accidental fall.

The present invention thus relates also to roping systems, typically including body harness systems such as those worn by rock climbers, or by law enforcement or military personnel, e.g., when rappelling down a cliff/wall or lowering via a rope from a hovering helicopter, and similar circumstances and situations. The shock absorber assembly 30 is adaptable for use in conjunction with an anchored rope, to ameliorate the fall force or impact shock imparted by the rope to a user in the event of a fall, especially an accidental fall. A rope is deployed by a user during a tactical, operational, or possibly recreational situation, to permit a controlled ascent or descent. The rope is attached to an anchor point, so to arrest (with the rope) the user's accidental fall.

When a person falls, his body stores energy. During a fall arrest, this energy is dissipated by elongation of the rope, and focused compression and/or stretching (usually painful, sometimes harmful) of the user's body. (If a belayer person is present, energy also is absorbed by displacement of the belayer's body; however, the present invention finds particularly beneficial use in the absence of a belayer, that is, wherein a single user has his rope connected directly to a fixed anchor point.) Stated succinctly, therefore, energy is transmitted to the belay chain in the form of force. This fall force is called the fall force or impact force. For the user, it is the impact experienced during fall arrest.

We presently are interested in the impact force transmitted to the climber and the redirect point or anchor point. The value of this force relates to all of the important factors in energy absorption, including but not limited to rope elongation and absorption by the climber's body. The impact force on a rope corresponds to the maximum force on the falling user. It may be calculated for various hypothetical falls by measuring a maximum force imparted to a metal mass under standard test conditions (impact force standards). It is desirable to minimize the fall force felt by the user at the time his fall is arrested.

Also of interest is the “theoretical fall factor,” a concept and principle known in the art. The fall factor is often used to quantify the severity of a climbing fall. The fall factor is the ratio of fall length to rope length. A theoretical fall factor F_(th) is calculated using the formula:

$F_{th} = \frac{{Fall}\mspace{14mu}{length}}{{Rope}\mspace{14mu}{length}}$ where “Fall length” is the length of the climber's fall, and “Rope length” is length of rope available or paid out between the anchor point and the climber. Additional information regarding fall factors and the calculation of fall factor can be found at, for example, https://www.bergfreunde.eu/fall-factor-calculator and https://www.petzl.com/US/en/Sport/Fall-factor-and-impact-force. The object of the present invention is to provide a means and mode for reducing the impact force felt by a user at a fall arrest, without regard for the fall factor of a given fall.

Attention is invited to FIG. 12 , showing the invention configured for use for human fall shock absorption. The user is depicted wearing a climbing harness of a type known in the art, including a waist belt or strap and thigh straps, as seen in the figure. The harness includes a belt 60 having a central front secure loop, to which a rated carabiner 62 is removably but severely connected according to convention. The user employs a rope 64 to attach himself to an anchor point 70. The anchor point 70 is seen in FIG. 12 to be fixed to a floor or ground surface, but as readily may be overhead to the user; the present apparatus and system finds beneficial use with an anchor point fixed at nearly any height relative to the user. The rope 64 is for safety against an accidental fall by the user. It is noted, however, that the rope 64 may be, due to the user's preference in the circumstance, of a type that is comparatively stretch-resistant (such as an aramid fiber rope—not always in common use in roped tactical operations). The rope 64 may be, by way of non-limiting example, a Technora® rope of 9.5 mm diameter. Stretch-resistant rope contributes near no shock absorption in the event of a fall, so the use of the presently disclosed system is advantageously suggested with such a rope.

This alternative embodiment and usage include the shock absorber assembly 30 to the distal end of which the rope 64 is attached. A quick-release mechanism 66 may be used to connect the proximate end of the shock assembly 30 to the carabiner 62. The quick-release device 66 may be, for example, a “pelican” hook type of quick-release device known in the tactical and recreation rope climbing arts. As shown in FIG. 12 , when the shock absorber assembly 30 is in use, the quick-release device 66 is reliably but releasably connected to the rated carabiner 62 that is connected to the harness's main belt loop. In alternative use according to user decision, the quick-release may be releasably connected directly to the harness's main belt loop.

Referring to FIG. 12 , therefore, it is seen that in the event the user falls down from his position, his fall is arrested by the rope 64. The resulting fall force is transmitted, by the rope 64, to the user's harness (at the main central loop on waistband or belt 60, via the carabiner 62) and to the anchor point 70, but is ameliorated by the action of the shock absorber system 30 described hereinabove. It is noted that in this mode of use, the shock absorber assembly 30 preferably incorporate only a single absorber unit 32. The tensile rupture strength of an absorber unit 32 employed in this alternative mode and means of fall force shock absorption can be significantly less than 600 lbs. (i.e., at least 600 lbs. in the case for the tandem parachute mode and means), as adapted to the circumstances of particular use.

After a fall has been arrested, the resilient absorber unit 32 rebounds elastically to its former “rest” or standard condition and shape. Thus, the present assembly 30, including the absorber unit 32, is contemplated to be re-usable in serial tactical, industrial, or recreational operations. The shock absorber assembly 30 is ideal in all the mentioned (tactical, industrial, or recreational operations) scenarios not only can it receive multiple falls but will be resistant to saltwater environments from maritime operation, and petrol chemicals leaking from rotary or fix-wing aircrafts, etc.

Although the invention has been described in detail with particular reference to these preferred embodiments, other embodiments can achieve the same results. In this description, specific details are set forth, such as specific materials, structures, processes, etc., in order to provide a thorough understanding of the present invention. However, as one having ordinary skill in the art of tandem cargo parachuting would recognize, the present invention can be practiced without resorting strictly only to the details specifically set forth. In other instances, well-known concepts and compositions have not been described in detail, in order not to unnecessarily obscure the present invention.

Only some embodiments of the invention and but a few examples of its versatility are described in the present disclosure. It is understood that the invention is capable of use in various other combinations and is capable of changes or modifications within the scope of the inventive concept as expressed herein. Modifications of the invention will be obvious to those skilled in the art and it is intended to cover by the appended claims all such modifications and equivalents. 

I claim:
 1. A shock absorber assembly comprising: at least two separate stretchable absorber units comprised of a thermoplastic elastomer and each absorber unit further comprising: a first end attachment portion; a second end attachment portion; at least one fastener aperture defined through the first end attachment portion; and at least one other fastener aperture defined through the second end attachment portion; at least three parallel intermediate joinder sections integrally joining and extending between the first end attachment portion and the second end attachment portion; and a limiter strap having a first looped end, a second looped end, and a maximum length; a first connector releasably disposed through the limiter strap's first looped end and through fastener apertures defined through the first end attachment portions of the at least two stretchable absorber units; and a second connector releasably disposed through the limiter strap's second looped end and through fastener apertures defined through the second end attachment portions of the at least two stretchable absorber units.
 2. The shock absorber assembly according to claim 1 adapted for use during a tethered tandem cargo parachuting operation, further comprising a cargo tether operatively connectable to and extendible from the first connector.
 3. The shock absorber assembly according to claim 2 wherein the at least two separate absorber units comprise low-stretch absorber units each having a tensile strength of about 6,400 psi.
 4. The shock absorber assembly according to claim 2 wherein the at least two separate stretchable absorber units comprise high-stretch absorber units each having a tensile strength of about 5,500 psi.
 5. The shock absorber assembly according to claim 1 wherein the at least two separate stretchable absorber units comprise at two absorber units of differing tensile strengths.
 6. The shock absorber assembly according to claim 5 wherein the at least two absorber units comprise a low-stretch absorber unit having a tensile strength of about 6,400 psi and capable of 430% elongation, and a high-stretch absorber unit having a tensile strength of about 5,500 psi and capable of 500% elongation.
 7. The shock absorber assembly according to claim 2 further comprising a cargo harness wherein the second connector is operatively connectable to the harness.
 8. The shock absorber assembly according to claim 7 wherein the at least three parallel intermediate joinder sections comprises four cylindrical joinder sections.
 9. The shock absorber assembly according to claim 1 wherein the at least two stretchable absorber units comprises a low-stretch absorber unit having a low-stretch absorber maximum breaking length less than the limiter strap's maximum length.
 10. The shock absorber assembly according to claim 9 wherein the low-stretch absorber unit defines an inner fastener aperture and an outer fastener aperture in each of its end attachment portions.
 11. The shock absorber assembly according to claim 1 wherein the at least two stretchable absorber units comprises a high-stretch absorber unit having a high-stretch absorber maximum breaking length less than the limiter strap's maximum length.
 12. The shock absorber assembly according to claim 1 wherein when in use the shock absorber assembly comprises: the limiter strap folded against itself into a compact bale; and means for releasably maintaining the folded limiter strap in the compact bale.
 13. The shock absorber assembly according to claim 12 wherein the means for releasably maintaining comprises a flap, connected to the limiter strap, having complementary fasteners thereon, wherein in use the flap is wrapped around the folded strap and the at least one stretchable absorber unit and releasably secured by the fasteners.
 14. The shock absorber assembly according to claim 12 wherein the means for releasably maintaining comprises at least one frangible band wrapped around the folded strap.
 15. A shock absorber assembly for use with a tethered tandem cargo parachute system including a cargo tether and a cargo harness attached to a cargo bundle, the shock absorber assembly comprising: at least one stretchable absorber unit comprised of a thermoplastic elastomer and further comprising: a first end attachment portion; a second end attachment portion; at least one fastener aperture defined through the first end attachment portion; and at least one other fastener aperture defined through the second end attachment portion; at least three intermediate parallel cylindrical joinder sections integrally joining and extending between the first end attachment portion and the second end attachment portion; and a limiter strap having a first looped end, a second looped end, and a maximum length; a first connector releasably disposed through the limiter strap's first looped end and through the at least one fastener aperture defined through the first end attachment portion, and operatively connectable with the cargo tether; and a second connector releasably disposed through the limiter strap's second looped end and through the at least one fastener aperture defined through the second end attachment portion, and operatively connectable with the cargo harness; wherein the at least one fastener aperture defined through the first end attachment portion comprises a first inner fastener aperture and a first outer fastener aperture; and wherein the at least one other fastener aperture defined through the second end attachment portion comprises a second inner fastener aperture and a second outer fastener aperture.
 16. The shock absorber assembly according to claim 15 wherein the at least three intermediate joinder sections comprises four cylindrical joinder sections.
 17. The shock absorber assembly according to claim 15 wherein the at least one stretchable absorber unit comprises two, three, or four separate stretchable absorber units.
 18. The shock absorber assembly according to claim 17 wherein: when in use the shock absorber assembly comprises the limiter strap folded against itself into a compact bale; and means for releasably maintaining the folded limiter strap in the compact bale.
 19. The shock absorber assembly according to claim 15 wherein the at least one stretchable absorber unit comprises at least two stretchable absorber units, and wherein: the first connector is releasably disposed through a first inner fastener aperture of a first absorber unit and through a first outer aperture of at least a second absorber unit; and the second connector is releasably disposed through a second inner fastener aperture of the first absorber unit and through a second outer aperture of at least the second absorber unit.
 20. The shock absorber assembly according to claim 18 wherein: the means for releasably maintaining comprises a flap, connected to the limiter strap, having complementary fasteners thereon; and in use the flap is wrapped around the folded strap and around the stretchable absorber units, and releasably secured by the fasteners, until a time when the absorber units stretch under a tensile load thereby to cause the strap to unfold and the complementary fasteners to mutually detach. 